Nevertheless, under USA law it is likely that the typical

disclaimers of copyright or public domain dedications we see in the

Free Software world would be interpreted by courts as copyright

abandonment, leading to a situation in which the user effectively receives a

maximum grant of copyright freedoms, similar to a maximally-permissive

Free Software license.

The best example of software known to truly be in the public domain is software

that is published by the USA government.  Under

\href{http://www.law.cornell.edu/uscode/text/17/105}{17 USC 101 \S~105}, all

works published by the USA Government are not copyrightable in the USA.

\subsection{Why Copyright Free Software?}

If simply disclaiming copyright on software yields Free Software, then it

stands to reason that putting software into the public domain is the

easiest and most straightforward way to produce Free Software. Indeed,

some major Free Software projects have chosen this method for making their

software Free. However, most of the Free Software in existence \emph{is}

copyrighted. In most cases (particularly in those of FSF and the GNU

Project), this was done due to very careful planning.

Software released into the public domain does grant freedom to those users

who receive the standard versions on which the original author disclaimed

copyright. However, since the work is not copyrighted, any nontrivial

modification made to the work is fully copyrightable.

Free Software released into the public domain initially is Free, and

perhaps some who modify the software choose to place their work into the

public domain as well. However, over time, some entities will choose to

proprietarize their modified versions. The public domain body of software

feeds the proprietary software. The public commons disappears, because

fewer and fewer entities have an incentive to contribute back to the

commons. They know that any of their competitors can proprietarize their

enhancements. Over time, almost no interesting work is left in the public

domain, because nearly all new work is done by proprietarization.

A legal mechanism is needed to redress this problem. FSF was in fact

originally created primarily as a legal entity to defend software freedom,

and that work of defending software freedom is a substantial part of

its work today. Specifically because of this ``embrace, proprietarize and

extend'' cycle, FSF made a conscious choice to copyright its Free Software,

and then license it under ``copyleft'' terms. Many, including the

developers of the kernel named Linux, have chosen to follow this paradigm.

\label{copyleft-definition}

Copyleft,

which uses functional parts of copyright law to achieve an unusual result

(legal protection for free sharing) forms the core legal principle of these

licenses. It modifies, or ``hacks'' copyright law, which is usually employed to

strengthen the rights of authors or publishers, to strengthen instead the

rights of users.   %FIXME-URGENT: end

Copyleft is a legal strategy and mechanism to defend, uphold and propagate software

freedom. The basic technique of copyleft is as follows: copyright the

software, license it under terms that give all the software freedoms, but

use the copyright law controls to ensure that all who receive a copy of

the software have equal rights and freedom. In essence, copyleft grants

freedom, but forbids others to forbid that freedom to anyone else along

the distribution and modification chains.

% FIXME-URGENT: integrate

This ``reciprocity'' or ``share and share alike'' rule protects both

developers, who avoid facing a ``proprietized'' competitor of their project,

and users, who can be sure that they will have all four basic freedoms not

only in the present version of the program they use, but in all its future

improved versions.

% FIXME-URGENT: integrate

The unit of copyright law is ``the work''. In that sense, the ``work''

referenced by the licenses is anything that can be copyrighted or will be

subject to the terms of copyright law. The GNU licenses exercise their scope

fully. Anything which is ``a work'' or a ``work based on a work'' licensed

under GPL is subject to its requirements, including the requirement of

complete and corresponding source code, unless it is specifically

excepted. This principle often causes theoretical or speculative dispute

among lawyers, because ``the work'' is not a unit of computer programming. In

order to determine whether a ``routine'' an ``object'', a ``function'', a

``library'' or any other unit of software is part of one ``work'' when combined

with other GPL’d code, we must ask a question that copyright law will not

directly answer in the same technical terms.

The key here is that the GNU GPL licenses mean to ``plow fence row to fence

row'', covering every version of ``work based on the work'' recognized by local

copyright law, but no further.

%FIXME-URGENT: end

Copyleft is a general concept. Much like ideas for what a computer might

do must be \emph{implemented} by a program that actually does the job, so

too must copyleft be implemented in some concrete legal structure.

``Share and share alike'' is a phrase that is used often enough to explain the

concept behind copyleft, but to actually make it work in the real world, a

true implementation in legal text must exist. The GPL is the primary

\pagebreak[4]

\section*{How to Apply These Terms to Your New Libraries}

If you develop a new library, and you want it to be of the greatest

possible use to the public, we recommend making it Free Software that

everyone can redistribute and change. You can do so by permitting

redistribution under these terms (or, alternatively, under the terms of

the ordinary General Public License).

To apply these terms, attach the following notices to the library. It is

safest to attach them to the start of each source file to most effectively

convey the exclusion of warranty; and each file should have at least the

``copyright'' line and a pointer to where the full notice is found.

\begin{quote}

one line to give the library's name and a brief idea of what it does. \\

Copyright (C) year  name of author \\

This library is Free Software; you can redistribute it and/or modify it

under the terms of the GNU Lesser General Public License as published by

the Free Software Foundation; either version 2.1 of the License, or (at

your option) any later version.

This library is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public

License for more details.

You should have received a copy of the GNU Lesser General Public License

along with this library; if not, write to the Free Software Foundation,

Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

\end{quote}

Also add information on how to contact you by electronic and paper mail.

You should also get your employer (if you work as a programmer) or your

school, if any, to sign a ``copyright disclaimer'' for the library, if

necessary. Here is a sample; alter the names:

\begin{quote}

Yoyodyne, Inc., hereby disclaims all copyright interest in the program \\

`Gnomovision' (which makes passes at compilers) written by James Hacker. \\

signature of Ty Coon, 1 April 1990 \\

Ty Coon, President of Vice

\end{quote}

\chapter{The GNU General Public License, version 3}

\begin{center}

{\parindent 0in

Version 3, 29 June 2007

Copyright \copyright\  2007 Free Software Foundation, Inc. \texttt{http://fsf.org/}

\bigskip

Everyone is permitted to copy and distribute verbatim copies of this

license document, but changing it is not allowed.}

\end{center}

\begin{center}

{\bf\large Preamble}

\end{center}

The GNU General Public License is a free, copyleft license for

software and other kinds of works.

The licenses for most software and other practical works are designed

to take away your freedom to share and change the works.  By contrast,

the GNU General Public License is intended to guarantee your freedom to

share and change all versions of a program--to make sure it remains free

software for all its users.  We, the Free Software Foundation, use the

GNU General Public License for most of our software; it applies also to

any other work released this way by its authors.  You can apply it to

your programs, too.

When we speak of free software, we are referring to freedom, not

price.  Our General Public Licenses are designed to make sure that you

have the freedom to distribute copies of free software (and charge for

them if you wish), that you receive source code or can get it if you

want it, that you can change the software or use pieces of it in new

free programs, and that you know you can do these things.

To protect your rights, we need to prevent others from denying you

these rights or asking you to surrender the rights.  Therefore, you have

certain responsibilities if you distribute copies of the software, or if

you modify it: responsibilities to respect the freedom of others.

For example, if you distribute copies of such a program, whether

gratis or for a fee, you must pass on to the recipients the same

freedoms that you received.  You must make sure that they, too, receive

or can get the source code.  And you must show them these terms so they

know their rights.